1. Field of the Invention
The present invention relates to an image forming apparatus such as a laser printer capable of forming images on a front surface and a back surface of a sheet and a controlling method of this image forming apparatus, and particularly relates to an image forming apparatus having a both-face conveying portion for reversing surfaces of a sheet on one surface of which an image is formed and conveying the sheet to an image forming portion.
2. Related Background Art
There is a conventional image forming apparatus in which surfaces of a sheet on one surface of which an image is formed by an image forming portion is reversed and the sheet is again conveyed to the image forming portion and an image is formed on a back surface of the sheet.
For example, in an image recorder such as a laser printer as one example of the conventional image forming apparatus, a both-face conveying portion having a both-face conveying path for conveying the sheet to the image forming portion by reversing the surfaces of the sheet is optionally mounted to a relatively large-sized device operated at high speed and high in cost, and images are recorded to both surfaces of the sheet. Recently, a tendency to the requirement of a function for recording images to both surfaces of the sheet is increasing to save resources, etc. even in a laser printer, etc. made compact and operated at low speed and low in cost.
The conventional image recorder having such a both-face conveying portion has a one-face mode for forming an image on one surface of the sheet and a both-face mode for reversing by the both-face conveying portion the surfaces of the sheet on one surface of which an image is formed and conveying this reversed sheet to the image forming portion and forming an image on a back surface of the sheet.
Further, for example, a face-up tray is openably and closably arranged in an apparatus body to face-up-discharge the sheet on one surface of which the image is formed. In the one-face mode, the sheet is stored in a face-up state by opening this face-up tray.
When the sheet is stored in a face-down state in the one-face mode, the face-up tray is closed to form a sheet discharge path for conveying the sheet to a face-down storing portion arranged on an upper face of the apparatus body. Further, this face-up tray is closed in the both-face mode to form the sheet discharge path for conveying the sheet forming images on both surfaces thereof to the face-down storing portion and a conveying path to the both-face conveying portion.
However, when the sheet discharge path is formed by the face-up tray in this way, there is a case in which the sheet on one surface of which the image is formed is not conveyed to the both-face conveying portion but the sheet discharge path is jammed with the sheet when the face-up tray is opened in error particularly in the both-face mode.